1. Technical Field
The present invention relates to semiconductor devices and their fabrication.
2. Description of Related Art
Strained silicon p-type field effect transistors have been described which include a transistor channel in a region consisting essentially of silicon and source and drain regions which include embedded regions of silicon germanium at opposite (front and rear) ends of the transistor channel for applying a compressive stress to the silicon transistor channel region. Typically, the embedded silicon germanium regions are formed by epitaxial growth from a surface of an underlying silicon region. Similarly, n-type field effect transistors have been described which include a silicon transistor channel and embedded regions of silicon carbon at opposite front and rear ends of the transistor channel for applying a tensile stress to the transistor channel. However, silicon carbon regions are difficult to grow epitaxially without defect. In addition, difficulties are presented in integrating epitaxy processes for both silicon germanium and silicon carbon in one process for fabricating PFETs and NFETs on a substrate.
It would be desirable to provide a process for forming both PFETs and NFETs with channels provided in regions of strained semiconductor material.